This invention relates to an applicator for holding and applying a highly viscous fluid such as a correction fluid, a make-up fluid, an adhesive or a paint.
In an applicator having a spherical form of application member (application ball), a tip is attached to a neck formed at one end of a fluid tank which is filled with a fluid to be applied. The tip bears rotatably therein an application ball in such a way that the application ball may partly be exposed from the front edge thereof like a ball-point pen. The application ball is resiliently urged by a spring so as to bring the application ball into intimate contact with a caulked front edge of the tip, so as to allow the application ball and the front edge of the tip to form a valve structure for preventing the fluid to be applied from being discharged when the applicator is not used. When the application ball is pressed against a surface on which the fluid is to be applied, the application ball retracts against the resilience of the spring to provide a clearance between the application ball and the front edge of the tip, allowing the fluid to be deposited on a hidden portion of the application ball located within the tip for delivery through the clearance to the outside of the tip for application as the application ball is rolled. However, a fluid having a high viscosity cannot normally be fed fully to the surface of the application ball. Accordingly, the fluid tank is molded by blowing using a flexible material to be squeezable, and the fluid tank must be pressed between a user's fingers to increase the internal pressure of the fluid tank so as to allow the fluid to be more easily fed to the surface of the application ball with the aid of the thus increased pressure and be applied to the surface to be treated.
Meanwhile, in the case where the application member is rod-shaped, a tapered portion is formed at the middle of the application member. The tapered portion of the application member is resiliently urged by a spring to be brought into intimate contact with a caulked front edge of the tip to form a valve structure between the rod-shaped application member and a front edge of the tip, so that the fluid to be applied may not be discharged when the applicator is not in use. When the application member is pressed against the surface to be treated, the application member retracts against the resilience of the spring to provide a clearance between the tapered portion of the application member and the front edge of the tip. Again, the fluid tank must be pressed between a user's fingers so as to increase the internal pressure of the fluid tank in order to feed the fluid to the application member and apply the fluid to the surface to be treated.
As described above, the prior art applicators have the disadvantage that the handling thereof is more difficult since the fluid tank must be pressed between a user's fingers to increase the internal pressure of the tank for application of the fluid, and the further disadvantage that the production cost elevates since the fluid tank must be molded by blowing using a flexible material.
If a cap is designed to be able to be push-fitted to the neck of the fluid tank with the front edge of the tip being sealed with the inner barrel of the cap and to be able reduce the volume of the sealed space defined within the inner barrel, when the cap is engaged with the neck the internal pressure of the inner barrel can be increased. Accordingly, air in the inner barrel will flow into the fluid tank to increase the internal pressure of the fluid tank, and thus the fluid tank need not be pressed between a user's fingers for application of the fluid to be applied. However, since the application ball is resiliently urged by the spring, the application member must be retracted against the resilience of the spring so as to allow the air in the inner barrel to intrude into the fluid tank. Accordingly, the internal pressure of the inner barrel must be sufficiently increased. In other words, while the push fitting stroke of the cap in the state where the inner barrel thereof is sealing the front edge of the tip must be increased, the longer the inner barrel of the cap becomes, the more difficult the pressurizing operation becomes.